From 5cb29541603a97167a07afe8ac6bd59e863bf2d1 Mon Sep 17 00:00:00 2001 From: "Duncan P. N. Exon Smith" Date: Sat, 24 Sep 2016 20:42:02 +0000 Subject: [PATCH] Analysis: Return early for UndefValue in computeKnownBits There is no benefit in looking through assumptions on UndefValue to guess known bits. Return early to avoid walking their use-lists, and assert that all instances of ConstantData are handled here for similar reasons (UndefValue was the only integer/pointer holdout). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282337 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ValueTracking.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp index 827e2524915..7983240c3dd 100644 --- a/lib/Analysis/ValueTracking.cpp +++ b/lib/Analysis/ValueTracking.cpp @@ -1502,6 +1502,14 @@ void computeKnownBits(const Value *V, APInt &KnownZero, APInt &KnownOne, // Start out not knowing anything. KnownZero.clearAllBits(); KnownOne.clearAllBits(); + // We can't imply anything about undefs. + if (isa(V)) + return; + + // There's no point in looking through other users of ConstantData for + // assumptions. Confirm that we've handled them all. + assert(!isa(V) && "Unhandled constant data!"); + // Limit search depth. // All recursive calls that increase depth must come after this. if (Depth == MaxDepth) -- 2.50.1